Fire detection system



Feb. 8, 1966 J. E. LiNDBERG 3,234,537

FIRE DETECTION SYSTEM Filed May 5, 1964 2 Sheets-Sheet 1 Fig.1.

52 E 13. qmfi INVENTOR. JOHN E. Ll/VDBERG Feb. 8, 1966 J. E. LINDBERG 3,

FIRE DETECTION SYSTEM Filed May 5, 1964 2 Sheets-Sheet 2 United StatesPatent Ofiice 3,234,537 FIRE DETECTION SYSTEM John E. Lindberg, 1211Upper Happy Vailey Road, Lafayette, Calif. Filed May 5, 1964, Ser. No.365,128 11 Claims. (Cl. 340-229) This invention relates to improvementsin fire detection systems. This application is a continuation-in-part ofapplication Serial Number 252,730, filed January 21, 1963, nowabandoned.

Fire detection systems have long been prone to give false alarms. Whenthe system is installed on an airplane, the consequences of a falsealarm are very grave, because the pilot must immediately take drasticremedial action, including the jettisoning of fuel and the search atonce for a suitable place to land. Every false warning is very expensiveto an airline, and some false warnings result in crashes.

The present invention provides a fire detection system in which theprobability of the occurrence of a false warning is unusually low. Infact, it is nearly impossible to obtain a false warning from the firedetection system of this invention.

A preferred form of the invention entails the use of a fire detection ortemperature-sensitive sensor in connection with two sensor-actuatedswitches, one of which is normally open and one of which is normallyclosed. A power source and a warning device are connected in series withthe normally open switch, and the normally closed circuit is connectedin parallel with the warning means. In true operation, the sensorsimultaneously closes the normally open switch and opens the normallyclosed switch, so that the power source actuates the warning signal.However, when there is no true actuation, any short circuit around thenormally open switch that would ordinarily cause a false-warning type ofactuation of the warning device is nullified by the parallel connection,which provides a dead short through the normally closed switch aroundthe signal device, and thereby prevents the actuation of the signaldevice.

Addition advantages and features of the invention will appear from thefollowing description of a preferred form thereof.

In the drawings:

FIG. 1 is a circuit diagram of a fire detection system embodying theprinciples of the invention, with an actuator shown in elevation and insection, the vertical thicknesses of the members being greatlyexaggerated.

FIG. 2 is a circuit diagram of a modified form of system embodying theprinciples of the invention, showing also a modified actuator, inelevation and in section, thicknesses again being greatly exaggerated.

FIG. 3 is a circuit diagram showing how several of the sensor-respondercombinations of FIG. 2 can be placed in the same circuit with a singlepower source and a single warning device.

FIG. 4 is a circuit diagram of another modified form of the invention,another form of actuator being shown in elevation and in section,thicknesses again being greatly exaggerated.

The device shown in FIG. 1 includes a suitable temperature-detectingsensor for the purposes of this explanation, the sensor 10 may beconsidered as one like that described and claimed in my patentapplication Serial No. 102,622 filed April 10, 1961, now abandoned,namely, a tube closed at one end and containing some metallic hydrideand also a noble gas. This device responds to temperature increases byan increase in internal pressure. When the temperature reaches apredetermined warning level, the pressure within the sensor 11 andwithin a chamber 11 with which the interior of the sensor 10 communi-3,234,537 Patented Feb. 8, 1966 cates, reaches a predetermined levelwhich is used to actuate one or more pressure switches.

Here, the sensor 10 is shown connected to a responder 12 having a body13 and a pair of metal diaphragms 14 and 15. The diaphragm 14 has as itsactive portion a spherical segment or blister 16 which is actuated atthe critical pressure in the'chamber 11 to move upwardly toward aflattened position against an electrode 17. The diaphragm 15 has asimilar blister 18 which is actuated downwardly toward a flat positionat the same critical internalpressure, to move it away from an electrode19 with which it is normally in contact. The diaphragm blister 16 andelectrode 17 operate as a normally open switch, while the diaphragmblister 18 and electrode 19 form a normally closed switch. If theresponder body 13 is metal, the electrodes 17 and 19 are insulated fromthe body 13 by suitable insulating means such as ceramic tubes 20 and21.

The electrode 17 is connected by a wire 22 to a battery 23, and thebattery 23 is connected (preferably through a circuit breaker 23a) by awire 24 to a suitable Warning device, such as a signal lamp 25, althougha bell or any other type of warning device may be used. The lamp 25 maybe connected to a ground 26, and the body 13 is connected to a ground27, so that the lamp 25, battery 23, and normally open switch 16, 17 arein series. The electrode 19 is connected in parallel with the lamp 25 bya lead 28 which is located as close to the lamp 25 as possible, and bythe grounds 26 and 27. The sensor 10 is insulated from the responderbody 13 by a suitable insulator fitting 29. This enables the use of aseparate electrical circuit comprising a second battery 30, a switch 31,a portion 32 of the sensor 10 itself, and two ground points 33 and 34 toheat the sensor portion 32 electrically in order to cause a testactuation of the device.

The system of FIG. 1 operates as follows: when the internal pressure inthe sensor 10 and chamber 11 reaches its predetermined critical point,either due to the use of the test circuit 30, 31, 32, 33, 34, or byactual fire conditions, that pressure moves the two diaphragm blisters16 and 18 simultaneously, the diaphragm 16 moving upwardly to touch theelectrode 17 and thereby close its normally open circuit, the diaphragm18 moving downwardly away from the electrode 19 thereby to open itsnormally closed circuit. As a result, the circuit comprising thediaphragm 16, the electrode 17, lead 22, the battery 23, lead 24, thewarning device 25 and the two grounds 26 and 27 are in series and thewarning device is actuated; i.e., the lamp 25 will light.

Only the reading of the critical pressure will move these diaphragmblisters 16 and 18; so no false warning can come from that source. If,when the sensor pressure is below the critical level, the battery 23shouid get grounded into any other part of the circuit or anywhere onthe lead 22 or elsewhere, the lamp 25 wiil not be operated because thenormally closed switch 18, 19 is closed and simply shorts out thebattery 23 around the lamp 25. The circuit breaker 23a or a suitableload (see FIG. 4), prevents this shorting from draining the battery 23or damaging the wiring.

The system of FIG. 2 is substantially the same in principle as that ofFIG. 1. Here, a sensor 49 is provided with two terminal branches .1 and42 leading to separate and completely isolated responders 43, 44 whichmay be made from insulating material or may instead be insulated byinsulators 45, 46 from the sensor branches 41, 42. The responders 43, 44have respective conductive diaphragrns 47, 48. Normally, that is, at allinternal sensor pressures below the critical actuation level, thediaphragm 47 is spaced away from its associated electrode 50, but at thecritical pressure, the diaphragm 47 is closed against the electrode 50-Normally, the diaphragm 48 is closed against its electrode 51, but atthe critical pressure, the diaphragm 43 is moved away from theelectrode51.

A battery 52 is connected at one side to a ground 53 and at its otherside it is'connected (through a circuit breaker 49) by a lead54 to awarning device 55, which, in turn, connected by a lead 56 to theelectrode 50. The diaphragm 4'7 is grounded at a ground 57. A parallelcircuit for the normally closed switch 48, 51 is provided by alead 58 tothe diaphragm 48 and a lead to the electrode 51. Operation is about thesame as for the system of FIG. 1, and in the same way false warnings areavoided by the normally closed switch 48, 51 in parallel with the lamp55.

3 shows a plurality of devices like that of FIG. 2 with the electrodesof the normally open switches in the responders 43 being connected inparallel with each other by wires60, 61, 62, 63 and by the wires 64 and65 in series with the battery 52 and the warning device 55, while theelectrodes 51 of the normally closed switches are connected in serieswith each other by wires 66, 6'7, 68, and 69 and in parallel with thelamp 55 (by the line '70), to provided the saving orfalse-warning-prevention circuit.

FIG. 4 shows a system basically like that of FIG. 1, but with somesignificant differences. Here, the sensor 10 is connected to a novelresponder unit having two body members 10.1 and 102, both preferably ofmetal. The inner surface 103 of the body member 10.1 is preferably fiat,while the facing inner surface of the body member 102 is preferablyprovided with a shallow recess 104. A metal diaphragm 105 ishermetically brazed between the two body members 101 and 102 and has ablister 106, which is shown in its unstressed position. The body members101 and 102 have respective central openings 107 and 108.

Two ceramic tubes 111 and 112 are provided, both in order to provideinsulators, and the tube 111 is brazed to the body member 101 in theopening 107, by means of a brazing tube 113, while the tube 112 isbrazed to the body member 102 in the opening 108 by means of a brazingtube 114. An end closure member is brazed to the outboard end of theceramic tube 111 by a braze 116, and an end closure member 117 is brazedto the outboard end of the ceramic tube 112 by a braze 113. The endclosure members 115 and 117 are tubular and are brazed respectively totubular electrode members 121 and 122 by brazes 123 and 124. Theelectrode 121 need not be tubular, especially at its electrode end 125where it projects very, very slightly beyond the fiat surface 103; thatpart may be solid. If the electrode 121 is tubular, its outer end 126 issealed, as by a brazed wire 127. The tubular electrode 122 is brazed tothe sensor 10 and its interior passage 18% provides the communicationbetween the sensor 10 and the responder chamber.

The outer end 126 of the electrode 121 provides a terminal or contactmember, and this contact 126 is the one that is connected to the battery23, the other side of the battery being grounded, if desired, by asuitable ground 130. If desired, a return line, closed system may beused instead.

A second contact 131 is brazed to the body member 101, while a thirdcontact 132 may be brazed to the electrode 122. The contact or terminal132 is grounded by a ground 133. The contact or terminal 131 isconnected to the signal lamps 25, the other side of which is eitherdirectly connected to the battery 23 or is grounded at 134 to producethe same net effect.

The diaphragm blister 106 has two positions: a rest unstressed positionwhere it rests on an end 135 of the grounded electrode 132, and anactuated position when an increased pressure in the sensor 10 pushes itagainst the power electrode 126. The lamps 25 are lighted only when theblister 106 engages the power electrode 126. When the blister 106engages the grounded electrode 132,

the power circuit is open, and even if there should be a short circuitfrom it to the battery 23, the grounded electrode 132 would preventactuation of the lamps 25. The sensor 10 may include a heater testcircuit like that shown in FIG. 1.

These various forms of the invention each have their own uses and areillustrative of the principles of the invention, though not exhaustivethereof.

To those skilled in the art to which this invention relates, manychanges in construction and widely difiering embodiments andapplications of the invention will suggest themselves without departingfrom the spirit and scope of the invention. The-disclosures and thedescription herein are purely illustrative and are not intended to be inany sense limiting.

I claim:

1. A temperature detection system including in combination:

a source of electrical power,

an electrically actuated signal device in series with said source,low-resistance shunt means around said signal device to preventactuation thereof when the power is on,

normally closed freely openable and reclosable switch means in saidshunt means for opening said shunt means,

a temperature detector connected to said switch means for causing it toopen said shunt means at any time a predetermined critical temperatureis attained by said detector, said shunt means being closed again whensaid detector temperature drops below the critical value, and a secondnormally open switch means in series with said power source and saidsignal device, connected to said temperature detector for actuationthereby, being closed thereby at said predetermined criticaltemperature, both closure of said second switch means and opening ofsaid shunt means being required for actuation of said signal device.

2. A fire detection system, including in combination:

heat-detection sensor means for increasing pressure with temperature,first and second pressure-responsive switch means actuated at the samecritical temperature and both connected to said sensor means forpressure response,

said first pressure responsive switch being normally open,

said second pressure responsive switch being normally closed,

an electrically actuated warning device in parallel with said secondpressure responsive switch, and

a source of electrical potential, connected in series with said firstpressure responsive switch and said warning device.

3. The system of claim 2 having a second source of electrical potentialfor heating said sens-or means to the critical temperature, and switchmeans for actuating said second source at will to test the operabilityof the system.

4. The system of claim 2 wherein said first and second pressureresponsive means comprise two electrically conductive diaphragms in thesame electrically-conductive housing, and electrodes insulated from saidhousing.

5. The system of claim 4 wherein said housing is grounded and so is saidwarning device.

6. The system of claim 2 wherein said first and second pressureresponsive means comprise first and second electrodes facing each otherin a housing and a single electrically-conductive diaphragm betweenthem, normally resting against said second electrode and cooperatingwith it to form said second switch, said diaphragm being movable awayfrom said second electrode, to open said second switch, and against saidfirst electrode, with which it provides said first switch, to close saidfirst switch.

7. The system of claim 6 wherein said second electrode is grounded andso is said warning device.

8. The system of claim 2 wherein said first and second pressureresponsive means are in separate isolated housings and said sensor isbranched to communicate with both of them.

9. A fire detection system, including in combination:

a plurality of heat-detection sensor means for increasing pressure withtemperature,

a corresponding plurality of first and second pressure responsive switchmeans isolated electrically from each other and actuated at the samecritical temperature, one of each being connected to each said sensormeans for pressure response, each said first pressure responsive switchbeing normally open, each said second pressure responsive switch beingnormally closed,

a single electrically actuated warning device, and

a single source of electrical potential,

all said first switches being connected in parallel with each other andin series with said source and said warning device,

all said second switches being connected in series and in parallel Withsaid warning device.

10. A device for use in temperature detection with a sensor in which atemperature increase leads to a pressure increase, comprising,

a housing comprising facing first and second body members, each having acentral opening, said second body member having a recess,

a diaphragm sealed between said first and second body members and havinga blister normally in said recess,

first and second insulating tubes sealed in the respective centralopenings of the first and second body members respectively, and

first and second electrodes sealed to an outer portion of saidinsulating tubes,

said second electrode being tubular for connecting the interior of saidsensor to said diaphragm, an end of said second electrode extending intosaid recess and said blister normally resting against it,

said first electrode extending beyond said first housing member forcontact with said diaphragm when sensor pressure flexes said blisterthereagainst.

11. The device of claim 10 having means for grounding said secondelectrode and having said first electrode 15 providing first contactmeans and having second contact means electrically connected to saidhousing.

References Cited by the Examiner UNITED STATES PATENTS NEIL C. READ,Primary Examiner.

1. A TEMPERATURE DETECTION SYSTEM INCLUDING IN COMBINATION: A SOURCE OFELECTRICAL POWER, AN ELECTRICALLY ACTUATED SIGNAL DEVICE IN SERIES WITHSAID SOURCE, LOW-RESISTANCE SHUNT MEANS AROUND SAID SIGNAL DEVICE TOPREVENT ACTUATION THEREOF WHEN THE POWER IS ON, NORMALLY CLOSED FREELYOPENABLE AND RECLOSABLE SWITCH MEANS IN SAID SHUNT MEANS FOR OPENINGSAID SHUNT MEANS, A TEMPERATURE DETECTOR CONNECTED TO SAID SWITCH MEANSFOR CAUSING IT TO OPEN SAID SHUNT MEANS AT ANY TIME A PREDETERMINEDCRITICAL TEMPERATURE IS ATTAINED BY SAID DETECTOR, SAID SHUNT MEANSBEING CLOSED AGAIN WHEN SAID DETECTOR TEMPERATURE DROPS BELOW THECRITICAL VALUE, AND A SECOND NORMALLY OPEN SWITCH MEANS IN SERIES WITHSAID POWER SOURCE AND SAID SIGNAL DEVICE, CONNECTED TO SAID TEMPERATUREDETECTOR FOR ACTUATION THEREBY, BEING CLOSED THEREBY AT SAIDPREDETERMINED CRITICAL TEMPERATURE, BOTH CLOSURE OF SAID SECOND SWITCHMEANS AND OPENING OF SAID SHUNT MEANS BEING REQUIRED FOR ACTUATION OFSAID SIGNAL DEVICE.